The long-term objective of this project is to develop a new technology that will enable rapid, single-molecule detection and identification of DNA sequences present in a biological sample. The current effort will focus on detecting nucleic acid molecules labeled with varying sizes of nanoparticles by recording changes in ionic current through a small, nanometer-scale channel in a "nanopipette." Once this detection technology has been demonstrated, the labeled oligonucleotides can be hybridized to a test sample, the unhybridized labeled molecules removed, and the remaining labeled DNA molecules can be rapidly detected on a single-molecule basis through the nanopipette. This will result in an ultra-sensitive, rapid genotyping technology that can be used for point-of-care diagnostics. The diagnostics can include the detection of pathogens or the determination of a human genotype in a clinical sample. This nanopipette DNA detection technology will also pave the way for second-generation devices, which allow higher resolution detection and could be used for rapid, single-molecule DNA sequencing, eventually realizing the possibility of sequencing an entire human genome in a matter of seconds. In this effort, Stanford will develop and demonstrate this nucleic acid detection technology with the following Specific Aims: -Nanopipette fabrication and characterization -Labeling DNA with nanoparticles -Measurement of labeled DNA